I wanted to see if there was any real reason to get excited about these types of headers, so I asked PG if he had any dyno charts that might shed some light on the subject one way or the other. Here's what he came up with.

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The original factory headers are 40mm primary tubes. RD Sport experimented with two different designs of larger tube headers. Headers were produced in 42mm and 44mm primary tube configurations. A Tri-Y collector and 4:1 collector were also tested. The dyno chart immediately below will show only stock and Tri-Y configurations. Another dyno chart later on will show the comparison between Tri-Y and 4:1 collectors with and without ECU tuning. In the first dyno chart, there are five different RD Sport stroker motors: two with stock headers, and three with larger diameter Tri-Y headers.

Changing the header design to Tri-Y has a significant negative effect without proper ECU tuning. From looking at these charts, you can see a significant torque dip between 2600-4000 RPMs on all cars with the Tri-Y header design. Moral to the story, don't mess with the header design unless you really know what you're doing.

There's no significant performance difference between the stock 40mm headers and larger 42mm headers, although the 42mm headers do seem to produce a tiny amount more torque.

There seems to be a negative performance impact jumping from 40mm headers (or 42mm) up to 44mm headers. Moral to the story: bigger isn't better, sometimes it's worse.

"RS46-5" continued to develop the ECU tuning for the Tri-Y and 4:1 headers. This car was delivered to a well known SoCal BMW tuner. The goal was to use ECU tuning to elimitate the torque dip on the Tri-Y header design. So RS46-5 picks up with the dyno chart below, almost exactly where the dyno chart above left off. Before ECU tuning began, RS46-5 was flashed back to stock, then delivered for ECU tuning.

There are four different graphs on the dyno chart below:

"Factory ECU" is the baseline for RS46-5. This is where tuning started for the Tri-Y headers.

"Tri-Y Tune" is the best tuned version of RS46-5.

"4-1" Baseline picks up where "Tri-Y Tune" leaves off. The only difference is the replacement of the Tri-Y collector with the 4:1 collector.

"4-1 Custom Tune" was the best tuned version of the 42mm headers with 4:1 collector.

Here's what jumps out at me from this chart:

No matter how many attempts were made, the ECU tuning was not able to remove the torque dip caused by the Tri-Y collector of the headers.

The final ECU tuning of the Tri-Y actually had less torque below 3000 RPMs than before ECU tuning.

Changing the collector from Tri-Y to 4:1 immediately elimited the torque dip. This tells me that header configuration is critical, and some designs can actually significantly hurt performance.

Based on what I saw with these large tube headers, I would want to know the following before making any header decisions.

What is the primary tube size? 42mm seems to work and produces a tiny amount of torque, but doesn't produce any real power over stock. 44mm seems too big and appears to lose power.

Is ECU tuning required to run these headers? We've seen what happens both with and without ECU tuning with larger tube headers. The headers themselves seem to disrupt many of the power characteristics of the motor, and the charts above would indicate that some level of ECU tuning will be required.

If ECU tuning is required, who is going to do it? If it is, I'd want to know if the tuner is capable, as it appears that not all tuners are.

Excellent comparison. The stock headers are very efficient and flow very well. I'm very glad we were able to get actual R&D that shows the stock headers are more than capable to make power even on a fully built engine.

In all reality the guys at M really did a great job with this car from that magnificent S65, intake and even the stock exhaust really. It will be interesting to see what the headers that IND has from M24 will do though...

In all reality the guys at M really did a great job with this car from that magnificent S65, intake and even the stock exhaust really. It will be interesting to see what the headers that IND has from M24 will do though...

Why would those be any different? We've seen 40, 42, 44mm ID and different collectors and none showed a gain in power. Very hard to make a power gain when the OEM headers are already very efficient and have no cats. I don't see how INDs could be any different and make the claimed 27whp.

Why would those be any different? We've seen 40, 42, 44mm ID and different collectors and none showed a gain in power. Very hard to make a power gain when the OEM headers are already very efficient and have no cats. I don't see how INDs could be any different and make the claimed 27whp.

I agree it is a big claim to make, who knows what else they have been testing. We should know soon since Nate and Ilia have said that they will be out by the end of the year.

All I was saying is that it will be interesting to see what their results are with the claims that were made and the data we have seen here and before regarding the OEM set.

Why would those be any different? We've seen 40, 42, 44mm ID and different collectors and none showed a gain in power. Very hard to make a power gain when the OEM headers are already very efficient and have no cats. I don't see how INDs could be any different and make the claimed 27whp.

The RD Sport headers were a different design than stock. 24 Motorsport's headers a mimic the stock design with larger tubing and an improved merge collector.

IND has made no claims on power increases nor are they the manufacturer of the headers, they just quoted the numbers that the manufacturer stated. Also, I didn't interpret the numbers that 24 Motorsport gave as 27 WHP, I thought it was 27 CHP.

Anyway time will tell if there is a gain with these. You can be sure of one thing, if IND sells them they will be a good product and the gains if any, will be independently documented!!!

The RD Sport headers were a different design than stock. 24 Motorsport's headers a mimic the stock design with larger tubing and an improved merge collector.

I think that was assumed because that's the only way you can do a Tri-Y header in the first place. The purpose of the thread was to demonstrate that changing the header design can cost performance, sometimes cost a lot of it as we saw with the Tri-Y design. ECU tuning would be needed to fix it, and in the case of RS46-5, the tuner wasn't able to fix it after a week of "custom tuning."

But once you introduce ECU tuning into the equation, you're no longer talking about the gains of the headers alone; you're also talking about the gains of the ECU tuning. ECU tuning already gives you 15-20whp gains (17-24chp) without changing headers. So if ECU tuning is apart of the 27hp gains, then I think it's safe to say these headers are adding very little (if any) performance.

In case you're wondering if ECU tuning was part of M24's claimed 27whp gain, take a look at their own web page (quoted below):

First tests on the achievement test stand resulted in an increased output of 27 HP/22 Nm. Further the S65 specialized elbow union is a further small success in the fight against to high temperatures in BMW the M3 E90, BMW M3 E92 and BMW M3 GTS - we succeeded in lowering the exhaust gas temperatures by our specialized elbow union into combination with a software modification over up to 100° Celsius.

OK, so now we know ECU tuning was part of the gains and is also required. I just don't think any tuners will spend the time and R&D energy on a niche market that will only sell to a very small handful of people per year.

To my understanding it was IMG's intention to start a compendium of information on already available performance headers.

I understand that seeing a new product released to market can be very exciting and it's tough not to guess at any product's potential benefits and costs before hard data is available, but we've learned over the years that it's best to suspend judgement until production versions are available.

Of course playing with hypotheticals can be lots of fun and I would never attempt to discourage that!

Because talk turned to M24's new headers in this thread, I would like to reiterate that these pieces are still in the pre-release stages of R&D and although IND has quoted some preliminary figures directly from the manufacturer, as a company we will suspend judgement until a finished version is in our hands and available for testing.

Sorry to derail the thread! Hopefully this thread can turn into a comprehensive information database.

To my understanding it was IMG's intention to start a compendium of information on already available performance headers.

I understand that seeing a new product released to market can be very exciting and it's tough not to guess at any product's potential benefits and costs before hard data is available, but we've learned over the years that it's best to suspend judgement until production versions are available.

Of course playing with hypotheticals can be lots of fun and I would never attempt to discourage that!

Because talk turned to M24's new headers in this thread, I would like to reiterate that these pieces are still in the pre-release stages of R&D and although IND has quoted some preliminary figures directly from the manufacturer, as a company we will suspend judgement until a finished version is in our hands and available for testing.

Sorry to derail the thread! Hopefully this thread can turn into a comprehensive information database.

Ilia, of course withholding judgement until independent tests are conducted on stock cars without ECU tuning is the best way to go. Hopefully this is the exact type of scientific testing that IND plans to do to determine what gains the M24 headers achieve all by themselves and without any other mods influencing the results. Hopefully your tests will add to this database of S65 header knowledge.

Ilia, of course withholding judgement until independent tests are conducted on stock cars without ECU tuning is the best way to go. Hopefully this is the exact type of scientific testing that IND plans to do to determine what gains the M24 headers achieve all by themselves and without any other mods influencing the results. Hopefully your tests will add to this database of S65 header knowledge.

That is what I was getting at in my reply! I don't want to sound like an IND fanboy but I am quite sure IND will test these and post the numbers once a production set is available to them. They have never done me wrong or made false claims on anything I have bought from them..... Ilia has even steered me away from some products that were of interest to me because he felt they were a waste of money, and would offer no appreciable gains or were of sub-par quality.

That is what I was getting at in my reply! I don't want to sound like an IND fanboy but I am quite sure IND will test these and post the numbers once a production set is available to them. They have never done me wrong or made false claims on anything I have bought from them..... Ilia has even steered me away from some products that were of interest to me because he felt they were a waste of money, and would offer no appreciable gains or were of sub-par quality.

P.S.: Thanks for the translated link!!!

Im not trying to say anything bad about Ilia neither ,i know Ilia and hes one stand up person.from business,car enthusiast to knowledge. so im sure the testing will be done right by IND !

A very informative post! This goes to show how crucial and meticulous tuning every part of a NA engine can be!

I really wish someone would try out a stepped, equal-length, long-tube, 4-1 header for this car.

Thanks again for sharing. I'm looking forward to seeing how this data compares to Motorsport24's headers.

Word.

I suspect the reason the tri-Y headers didn't work is due to the uneven pulses of the 90 degree crank. Try-Y works well on typical 4 cylinders with even firing pulses. It's my understanding that 4 into 1 still makes more top end power when tuned well, even on a four cylinder.

As for the m24 and rd-sport headers, I don't think its accurate to speculate about the performance gains on an N/A application and compare those to an F/I application. In N/A cars, a larger diameter primary could produce negligible gains, or even power loss because with the increased diameter, because there is also a decrease in exhaust velocity once the piping diameter is too large. Bigger is not always better. In F/I, the opposite case may apply. I have seen an e9x m3 with F/I and custom-made headers installed, and the owner did report gains, however I never saw a dyno sheet to confirm. I think there would be gains at higher boost levels, however the gains on N/A, even if they were there, probably would not be worth the expense.

On the c63's m156, there are big gains because it comes stock with log-style manifolds. On the s62's, which already comes with equal- length headers, the only place for improvement probably would be increasing the diameter of the primaries or a set of long-tubes.

I think the issue IMG is bringing up here is the ECU tune. We already know that you can come close to 27hp with a tune. So how much added HP is being produced by the new headers?

I think the only fair test would be to take some of the full bolt-on cars that have intake filters, and full exhausts already, ECU tune, etc... the one's making close to 400hp, and then see if they have much gain from headers. Then do the same with the SC cars to see if the benefits are only realized on FI.

Also important to note, is peak HP is not the only factor to look at. Really depends on your application. If you have a full out race car that spends almost all time at high RPM it may be completely different than someone who drives their car on the street.